A member of the studio audience writes:
There seems to be a problem here. If I personally have no reasons not to lie, and doing so would overall benefit me, there can be no possible reason why I should not lie. (Suppose I am unbothered by the negative consequences that others would inflict on me for lying.) This results in an absurd situation in which it is "reasonable" for me to lie, while it is also reasonable for others to try to prevent me from lying.
I do not see this as an absurd situation. In fact, I think it is quite common.
Lying would still be counted as immoral in this case. It is still true that people generally have many and strong reasons to promote an aversion to lying. The person who lies can be condemned as evil for not having aversions that people generally have many and strong reasons to create through acts of condemnation. Yet, it may still be the case that he has no reason not to lie. People generally have failed to give him such a reason.
Fortunately, I think there is a solution to this problem, and this solution involves distinguishing between two different sorts of "oughts": "ought" in the non-moral sense, and "ought" in the ethical sense. We are using the term non-morally when we say something like "If you want your car to have a long life, you ought to change the oil frequently." "Ought" is being used in the ethical sense when we say something along the lines of "I understand that, while murdering that person might benefit you, you ought not to kill him."
Desirism allows for something very similar to what you write here. "I understand that, while murdering that person may benefit you, people generally have many strong reasons to apply forms if punishment (such as condemnation) to the reward-learning system of others as a way of inhibiting the desires that would motivate such an action."
However - i suspect you are wanting to assert some sort of Kantian categorical imperative - an "ought" that does not have a goal. It's "just wrong" and that is all there is to it.
"Ought" in this categorical sense does not exist. There is no such thing as "just wrong". All 'just wrong' claims, no matter how popular, are false.
Desires are the only reasons for action that exist. They are the only kinds we find any actual evidence for - found in their ability to explain and predict intentional actions. Desires are propositional attitudes that can be expressed in the form "desire that P". The goal of a desire that P is a state of affairs in which P is true. All of our behavior is goal directed - including praise and condemnation. All of our motivation comes from our own desires.
Your definition captures the categorical nature of moral statements, but at the cost if making them mythical entities of no relevance or importance in the real world. My use sacrifices the categorical element of moral ought, but allows moral claims to remain true an important. They are all about malleable desires that people have many, strong, and real interests in promoting.
There is a precedent for this in chemistry. It was proposed that atoms were made up of parts. It could have been argued that thus claim violated the essential meaning of the word 'atom'. The word comes from ancient Greece and means literally, "without parts". Chemists faced a choice. They could have kept the essential meaning and insisted that a huge number of claims made in chemistry before that point were false. Or it could drop this essential meaning and allow chemistry tp progress much as it had.
Please note that this choice in no way threatened the objectivity of chemistry.
Ethics faces the same choice. It can preserve the categorical element of moral term and render all moral claims false. Or it can abandon that element and allow moral claims to remain potentially true and important.
I opt for the second option.
It should go without saying what we desire the most is justice.
Actually, this is false.
We evolved dispositions towards those desires that brought our ancestors biological success. Desires for sex, desires for food and drink, desires for the protection of our offspring, aversions to that which increase the possibility of injury and illness (e.g, the view down a steep cliff or the smell of rotting flesh).
Plus we have some malleable desires - modified by experience (particularly the social norms we pick up as children in cultures that have widely varying amounts of justice and injustice).
Regardless of what your personal concept if justice may be, we can falsify this claim just by pointing out the massive differences in what different communities call "justice". This alone should disprove any claim that there is a thing called "justice that we desire the most.